Much of contemporary cephalometric methodology represents a confusion of dichotomies made up of conflicting concepts of craniofacial growth, unlimited systems of quantitation, contradictory methods of superimposing tracings, all generally unrelated to each other and perpetuated merely by tradition. What has occurred is that major clinical treatment rationales have been built upon erroneous concepts.
The time has long passed when the number of quantitative systems were limited only by the number of points, planes and geometric combinations one could devise. Gone are the days when the ever pressing goal was the discovery of some elusive statistically significant correlation of measurements, irrespective of their biologic rhyme or reason. Those who have lived with this tool in research and tried to apply cephalometrics to clinical practice have come to view such approaches with skepticism and criticism. All too often the philosophy was an outgrowth of a system of quantitation when in reality, the systems should have quantitated the philosophy. In this light, the method of the present invention, Basion Horizontal, is presented as a coherent interrelated concept which in its broadest sense is a totally integrated philosophy of orthodontic rationale.
The basic concept of the present invention was introduced in a serial growth study published in 1955 under the title "The Integration of Facial Skeletal Variants" by S. E. Coben, Am. J. Orthod 41: 407-434. In this publication, the concept of Basion Horizontal (BaH) was introduced and defined as the plane parallel to the Frankfort horizontal plane whose point of origin is Basion. As such, Basion Horizontal represents the foramen magnum plane of orientation. The craniofacial growth concept which Basion Horizontal represents was indicated in 1961 to be that growth of the cranial base and growth of the mandible as reflected away from the foramen magnum (Basion) and the vertebral column. "Growth Concepts", by S. E. Coben, Angle Orthod. 31: 194-201, 1961. The craniomaxillary complex housing the maxillary dentition is translated upward and forward away from Basion by cranial base growth whereas mandibular growth carries the mandibular dentition downward and forward (FIG. 1). The divergence of the two general vectors creates space for vertical facial development and eruption of the dentition. In 1966 these vectors were related to systems of craniofacial growth. " Growth and Class II Treatment", by S. E. Coben, Am. J. Orthod, 52: 5-26, 1966. See FIGS. 2 and 3. The cranial base vector represents the upward and forward spatial translation of the upper face by growth of the spheno-occipital synchrondosis as growth of the spheno-ethmoidal circum-maxillary suture system and the nasal septum increase the depth and height of the upper face. Because the mandible maintains a constant spatial relation to the foramen magnum, the lower face vector represents the total reflection of mandibular growth carrying the lower teeth downward and forward away from the cranial base.
In 1966 it was suggested that two growth illustrations were necessary because of the two distinct phases of craniofacial growth created by a change in the system of upper facial development after the approximate age of seven. Prior to age seven, growth of the upper face is dominated by the nasal septum, the eyeballs, and the spheno-ethmoidal circum-maxillary suture system which creates space for the erupting maxillary molars. Bone apposition and remodeling resorption appears to be a minor secondary growth system at this time. At the age of seven, the growth system of the upper face changes with the closure of the spheno-ethmoidal suture. After the age of seven, the sella-frontale dimension stabilizes whereas the thickness of the frontal bone begins to increase by surface apposition and remodeling until maturity. The interpretation is that after the age of seven, the primary system of spheno-ethmoidal circum-maxillary sutural growth of the upper face is replaced by a primary system of surface apposition and remodeling resorption. Prior to age seven, space for the erupting upper molars is created by growth of the spheno-ethmoidal circum-maxillary suture system. After the age of seven, space must be created for the upper 2nd and 3rd molars by maxillary alveolar apposition as the maxillary molars erupt downward and forward to create retromolar space.
In 1979 a coordinate tracing film was suggested to express the growth concept both quantitatively and graphically. "Basion Horizontal Coordinate Tracing Film", by S. E. Coben, Am. J. Orthod. 13: 598-605, 1979. See FIG. 4. The coordinate grid was enlarged 8% to compensate for a standard cephalometric X-ray enlargement of 8%.